Development of imaging techniques of tissue characterization by means of time domain microwave computed tomography

时域微波计算机断层扫描组织表征成像技术的发展

基本信息

批准号：
12558105
负责人：
MIYAKAWA Michio
金额：
$ 8.45万
依托单位：
NIIGATA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

1. Conclusions of the study : Feasibility of microwave imaging using measurement techniques in time domain has been investigated. Time domains measurement techniques are used in this study for discriminating the wave components that transmitted on the straight path between two antennas from the scattered- or reflected wave components. This is a similar technique to CP-MCT in which the straight path between two antennas is discriminated by use of the techniques in frequency domain measurement of a chirp radar.The developed experimental system of Time Domain Microwave Computed Tomography (TD-MCT) that is consisted of a vector network analyzer and microwave scanner and measures S21 in the frequency range from 0.8 GHz to 4.2 GHz. Transmission time between two antennas can be time domain signal is determined by the reflected waves made by placing a metal plate in front of the antenna aperture. Accordingly, the signal which has a specific time interval corresponding to the straight path betw … More een two antennas can be excised from the observed signal to make projection data in frequency domain. This image reconstruction procedure is repeated at every 500 MHz in the frequency range from 1 GHz to 4 GHz. The major differences were observed in the signal to noise ratio and amount of unavoidable artifacts caused by interference among the diffracted- and transmitted-waves. In image reconstruction with 1 GHz bandwidth, the image reconstructed by use of the frequency components from 1 GHz to 2 GHz exhibits the most excellent quality. It is concluded that the CP-MCT that was designed at 1 GHz to 2 GHz has been properly designed. The estimated spatial resolution of TD-MCT shows the same value with that of CP-MCT.2. Practical significance of time domain microwave computed tomography : Generally speaking, any scanners of microwave computed tomography have to make measurement in bolus saline solution by immersing the antennas and biological object for impedance matching between them. Saline solution shows similar permittivity values with biological tissues in the frequency range of microwave imaging. The advantages of time domain measurement are derived most effectively by increasing the bandwidth of the signal as much as possible. On the other hand, it is hard to increase the frequency of tomographic measurement because transmission loss is increased abruptly when frequency increases. It is also hard to realize the antenna with a very wide bandwidth, for example more than 3 GHz in saline solution. CP-MCT extracts straight path transmission components from transmitted waves in frequency domain and TD-MCT does the same thing in time domain. However, CP-MCT can do it by measuring very low frequency signal which is lower than 1 kHz or less. This is an easy task as compared to the measurement procedure in time domain. It is considered that the advantages of TD-MCT will be found when spectral information can be used effectively. Less

1。研究的结论：已经研究了使用测量技术在时域中进行微波成像的可行性。本研究中使用了时域测量技术来区分从散射的波或反射波组件之间在两个天线之间传输的波部成分。这是一种与CP-MCT相似的技术，在该技术中，两个天线之间的直路是通过在频域中使用这些技术在chirp雷达的测量中使用的。两个天线之间的传输时间可以是时域信号，这是由将金属板放在天线孔的前面制成的反射波确定的。根据具有特定时间间隔的信号，与直接路径相对应……从观察到的信号中可以超过更多的两个天线，以在频域中制作投影数据。此图像重建过程在从1 GHz到4 GHz的频率范围内每500 MHz重复。在信号与噪声比和由衍射波和透射波之间的干扰引起的不可避免的伪像的量中观察到了主要差异。在具有1 GHz带宽的图像重建中，通过使用从1 GHz到2 GHz的频率组件重建图像表现出最出色的质量。结论是，以1 GHz至2 GHz设计的CP-MCT已正确设计。 TD-MCT的估计空间分辨率与CP-MCT.2的值相同。时域微波计算机断层扫描的实际意义：一般而言，任何微波计算机断层扫描的扫描仪都必须通过浸入天线和生物学对象以使其之间的阻抗匹配来对牛肉盐溶液进行测量。盐溶液在微波成像的频率范围内显示出与生物组织相似的介电性值。时间域测量的优点是通过尽可能增加信号的带宽来得出的。另一方面，很难增加层析成像测量的频率，因为当频率增加时，传输损失突然增加。也很难用非常宽的带宽实现天线，例如盐溶液中的3 GHz以上。 CP-MCT提取物从频域中的传输波和TD-MCT中的直路传输组件在时域中执行相同的操作。但是，CP-MCT可以通过测量低于1 kHz或以下的非常低的频率信号来做到这一点。与时域中的测量程序相比，这是一项容易的任务。据认为，当可以有效地使用光谱信息时，将发现TD-MCT的优势。较少的